The two groups of squares have parallel opposite sides and equal four sides; All four angles are 90 degrees; Diagonal lines are perpendicular, bisected and equal to each other, and each diagonal line bisects a set of diagonal lines.
A group of parallelograms with equal adjacent sides and a right angle is called a square. A group of rectangles with equal adjacent sides is called a square, and a diamond with an angle of 90 is called a square. Square is a special form of rectangle and diamond.